1. Technical Field
The present invention relates to a wireless communication apparatus, a wireless communication system and a wireless communication method which perform an information communication using a wireless signal.
2. Background Art
In recent years, such video apparatus as door phones and security cameras which use wireless communication have come to be developed because they can be installed easily. Among general TV door phone systems are ones which include a camera-equipped entrance slave unit, a monitor-equipped in-room master unit, and a monitor-equipped wireless slave unit. In such TV door phone systems, the camera-equipped entrance slave unit and the monitor-equipped in-room master unit are wire-connected to each other. When the call button of the camera-equipped entrance slave unit is pushed, a call sound is generated by the monitor-equipped in-room master unit, and at the same time, an image taken by the camera-equipped entrance slave unit is displayed on the monitor-equipped in-room master unit. The monitor-equipped in-room master unit sends, to the monitor-equipped wireless slave unit, using a wireless signal, a call signal and the image that has been received from the camera-equipped entrance slave unit, whereby a call sound is also generated by the wireless slave unit and the same image as displayed on the monitor-equipped in-room master unit is displayed on the monitor-equipped wireless slave unit.
Also in the case of security cameras, easy-to-install wireless security camera systems in which a wireless communication is performed between a camera and a monitor are being developed because wiring construction work is necessary if the camera and the monitor are wire-connected to each other.
For example, JP-A-2007-13539 discloses a door phone system in which even when an outside communication or an extension communication of a cordless phone and a door phone call have occurred simultaneously, the probability of occurrence of a busy state due to insufficiency in wireless communication resources is lowered and the user can be notified of both calls. JP-A-2005-295368 discloses that image data is transmitted plural times and that not only a control signal but also image data is transmitted using a time slot for transmission of a control signal. JP-T-2001-502488 discloses that a downlink is given a broader bandwidth than an uplink and a mobile station sends a retransmission request using a one-slot bandwidth.